JP6440670B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar lighting device.

  As a lighting means of a liquid crystal display panel, a sidelight type planar illumination device (backlight) in which a light source that emits white light is disposed along a side end surface of a light guide plate is widely adopted. Such a planar lighting device has been required to be thin, high brightness, uniform brightness, etc., but the demand for improving the uniformity of the color tone of the emitted light is also increasing. (For example, refer to Patent Document 1 and Patent Document 2).

JP 2005-347010 A JP 2012-94283 A

  However, recently, with the high definition of the liquid crystal display panel and the thinning and enlargement of the light guide plate, further reduction of color unevenness occurring on the side opposite to the light source side of the light guide plate has become a problem. In addition, it has been necessary to adjust the color tone on the light guide plate partially or locally.

  The present invention has been made in view of the above, and an object thereof is to provide a planar lighting device that partially suppresses color unevenness generated in a light guide plate and is excellent in uniformity of color tone of emitted light. With the goal.

In order to solve the above-described problems and achieve the object, a planar lighting device according to one embodiment of the present invention includes a light emitting diode and a wavelength conversion material that emits light when excited by light emitted from the light emitting diode. In a planar illumination device comprising: a light source that emits light; a light incident end surface that is an end surface on which the light source is disposed; and a light guide plate that has an emission surface that emits light incident from the light incident end surface. The light guide plate reflects light emitted from the wavelength conversion material and light emitted from the light emitting diode on at least one of the emission surface or the back surface opposite to the emission surface , and light emitted from the wavelength conversion material. Further, a light diffusing portion that mainly scatters light emitted from the light emitting diode is provided.

  The planar illumination device according to an aspect of the present invention is characterized in that the light diffusing portion is provided in a region close to a termination surface facing the light incident end surface.

  Further, in the planar illumination device according to one aspect of the present invention, the light diffusing unit includes fine unevenness that mainly causes Rayleigh scattering of light emitted from the light emitting diodes rather than light emitted from the wavelength conversion material. Features.

  The planar illumination device according to an aspect of the present invention is characterized in that the light diffusion portion has a transition region in which the area density of the fine unevenness gradually increases as the distance from the light incident end surface increases.

  The planar illumination device according to an aspect of the present invention is characterized in that the light diffusing unit has a region in which the area density of the fine unevenness increases or decreases along the light incident end surface.

  In the planar illumination device according to one aspect of the present invention, the light diffusing portion includes the fine unevenness smaller than a wavelength of light emitted from the light emitting diode.

  In the planar lighting device according to one embodiment of the present invention, an average height of the fine unevenness is smaller than a wavelength of light emitted from the light emitting diode.

  In the planar illumination device according to one aspect of the present invention, the light emitting diode is a blue light emitting diode that emits blue light, and the wavelength conversion material is excited by the blue light and is more than the blue light. It is a phosphor that emits light having a long wavelength.

  The planar illumination device according to the present invention has the effect of partially suppressing color unevenness generated in the light guide plate and being excellent in the uniformity of the color tone of the emitted light.

FIG. 1 is a diagram schematically illustrating a configuration of a planar illumination device according to the embodiment. FIG. 2 is a diagram schematically illustrating a configuration of the planar illumination device according to the embodiment. FIG. 3 is a schematic view showing a state in which fine irregularities are formed in a part of a mold for injection molding a light guide plate. FIG. 4 is a schematic view showing a state where fine irregularities formed on the mold are transferred to the light guide plate. FIG. 5 is a schematic diagram illustrating the operation of the light guide plate. FIG. 6 is a diagram illustrating an example of an image obtained by measuring the fine irregularities formed on the back surface of the light guide plate with a laser microscope. FIG. 7 is a diagram showing a roughness curve measured in a region where fine irregularities are not formed. FIG. 8 is a diagram showing a roughness curve measured in a region where fine irregularities are formed. FIG. 9 is a diagram illustrating a chromaticity diagram showing a difference in chromaticity depending on whether or not the present invention is applied. FIG. 10 is a graph showing a difference in chromaticity difference depending on whether or not the present invention is applied.

  Hereinafter, a planar lighting device 10 according to an embodiment of the present invention will be described with reference to the drawings. In each of the drawings shown below, the shape, size, and the like of each component are exaggerated as appropriate in order to facilitate understanding of the present invention. Further, in the accompanying drawings, when two components are illustrated so as to be adjacent to each other through a space, the space is inserted or exaggerated for easy understanding of the present invention. It is shown that the configuration of the present invention does not depend on the presence or absence of spaces between adjacent components or, if present, their dimensions.

  1 and 2 are diagrams schematically illustrating a configuration of a planar illumination device 10 according to the embodiment. FIG. 1 is a perspective view of the planar illumination device 10 as viewed obliquely from above, and FIG. 2 is a side view of the planar illumination device 10.

  The configuration example of the planar illumination device 10 illustrated in FIGS. 1 and 2 is a configuration of a so-called sidelight type backlight including a light guide plate 21 and a plurality of light sources 11 on a side end surface of the light guide plate 21. Here, the light source 11 is, for example, an LED (light emitting diode) that emits white light, and a so-called side view type LED that is suitable for being disposed on the side end surface of the light guide plate 21 is used. . In general, the LED as the light source 11 is mounted on an unillustrated FPC (Flexible Printed Circuit Board). Note that the FPC is arranged in parallel to a main surface (described later) of the light guide plate 21.

  In general, LEDs that emit white light that circulate in general have blue light emitting diodes that emit blue light sealed with a transparent resin to which a yellow phosphor that emits yellow light when excited by the blue light is added. The configuration is adopted. Therefore, the LED that emits typical white light that circulates in general does not have a flat emission spectrum, but has a pseudo peak that has an intensity peak in blue light emitted from a blue light emitting diode and yellow light emitted from a yellow phosphor. It emits typical white light.

  As a result, the color unevenness in the general planar illumination device 10 results in an intensity ratio between the blue light emitted from the blue light emitting diode and the yellow light emitted from the yellow phosphor, and the blue light and the yellow light By adjusting the intensity ratio locally, color unevenness in the planar illumination device 10 can be improved.

  In addition, the method of improving the color unevenness in the planar illumination device 10 by locally adjusting the intensity ratio of blue light and yellow light is widely useful for the general planar illumination device 10, The application of the present invention is not limited to this. From the viewpoint of ease of understanding and usefulness, the embodiment described below is an implementation that improves color unevenness resulting in an intensity ratio of blue light emitted by a blue light emitting diode to yellow light emitted by a yellow phosphor. Although it is a form, the scope of application of the present invention is that light emitted from a light emitting diode and light emitted from the light emitting diode and having a wavelength longer than the wavelength of blue light (not limited to yellow light, for example, green light and red light) A planar shape using an arbitrary light source 11 (for example, a light source 11 including a plurality of types of light emitting elements) including a light source 11 having a wavelength conversion material (phosphor, quantum dots, etc.) that emits light) and emitting white light. In general, the unevenness of color in the planar illumination device 10 can be improved by locally adjusting the intensity ratio of light having a predetermined wavelength by appropriately modifying the illumination device 10 and the present embodiment.

  As shown in FIGS. 1 and 2, the light guide plate 21 included in the planar illumination device 10 has a substantially plate shape as a whole, and includes two main surfaces and four end surfaces. The light guide plate 21 is made of a transparent material such as polycarbonate resin.

  Here, for ease of explanation, of the four end surfaces, the end surface on which the light source 11 is disposed is referred to as a light incident end surface 22, and the end surface facing the light incident end surface 22 is referred to as a termination surface 23. Of the two main surfaces, a main surface configured to emit light incident from the light incident end surface 22 in a planar shape is an output surface 25, and a main surface opposite to the output surface 25 is a back surface 24. .

  The planar lighting device 10 shown in FIGS. 1 and 2 includes a light incident wedge portion 27 and an emission portion 28. The light incident wedge portion 27 is provided on the light incident end surface 22 side of the light guide plate 21, and is formed such that the thickness of the light guide plate 21 decreases as the distance from the light incident end surface 22 increases. The light incident wedge portion 27 contributes to reducing the thickness of the light guide plate 21 in the light emitting portion 28 while ensuring a large light incident end surface 22 so that light from the light source 11 can be easily incident. In the present invention, the light incident wedge portion 27 is not an essential configuration. However, when the light incident wedge portion 27 is formed, due to the structure, a region near the light incident wedge portion 27 or near the light incident end surface 22 (light incident end surface 22). Color unevenness (a region from the center to the light guide direction) tends to be yellowish (for convenience, it is also referred to as “incident color unevenness of light”). Therefore, when the light incident wedge portion 27 is provided on the light guide plate 21, the light diffusion portion R according to the present invention, which will be described later, is disposed near the light incident wedge portion 27 on at least one of the emission surface 25 or the back surface 24. By providing it in the region near the light incident end face 22, the effect of the light diffusion portion R is effectively exhibited.

  An effective emission area E is defined on the emission surface 25, and light shielding means is applied to a region outside the effective emission area E of the main surface on the emission surface 25 side, so that unintended light (stray light) is emitted. Prevents leakage. Here, for the verification experiment described later, the coordinates in the effective emission region E are defined. As shown in FIGS. 1 and 2, the coordinates d are set in a direction away from the light incident end face 22 in the vertical direction with the light incident end face 22 as a reference. This coordinate d can be considered to substantially correspond to the distance that the light incident from the light incident end face 22 propagates through the light guide plate 21. The distance based on the coordinates d may be referred to as a light incident reference distance d.

  On the back surface 24 of the light guide plate 21, a large number of dots (optical path changing means) projecting hemispherically from the light guide plate 21 are arranged. These dots intentionally change the reflection angle of light on the back surface 24 of the light guide plate 21 so that the light reflected on the back surface 24 of the light guide plate 21 is emitted from the light exit surface 25 of the light guide plate 21. Is adjusted. Therefore, the arrangement of the dots on the back surface 24 of the light guide plate 21 is an important factor affecting the intensity distribution of the light emitted from the emission surface 25, and is determined by prior design.

  Since the light amount propagating through the light guide plate 21 decreases as the distance from the light incident end surface 22 decreases, generally, the dot arrangement density on the back surface 24 of the light guide plate 21 increases as the distance from the light incident end surface 22 increases. . In addition, the specific example of the dot formed in the back surface 24 of the light-guide plate 21 can be confirmed with the microscope picture of the back surface 24 of the light-guide plate 21 referred later.

  As shown in FIGS. 1 and 2, the light guide plate 21 provided in the planar illumination device 10 is provided with a light diffusion portion R on the back surface 24. The light diffusing unit R is configured to mainly scatter light emitted from the light emitting diode rather than light emitted from the phosphor in the light source 11.

  In the example of the planar illumination device 10 shown in FIGS. 1 and 2, the light diffusion portion R is provided in a band shape along the termination surface 23 in a region near the termination surface 23. This is because, in the example of the planar lighting device 10 shown in FIGS. 1 and 2, color unevenness in a region close to the end surface 23 (also referred to as “end color unevenness” for convenience) is improved. Therefore, the light diffusing unit R can appropriately change the arrangement position according to the region where the color unevenness to be improved occurs. For example, it can be provided not only in the region near the end surface 23 but also in the region near the light incident end surface 22. As described above, color unevenness may occur even in a region close to the light incident end face 22, and this color unevenness can be improved by providing the light diffusion portion R in a region close to the light incident end face 22.

  Further, in the example of the planar lighting device 10 shown in FIGS. 1 and 2, the light diffusion portion R is provided on the back surface 24, but may be provided on the exit surface 25, or the back surface 24 and the exit surface 25 may be provided. You may provide in both. That is, it can be said that the light diffusing portion R may be provided on at least one of the emission surface 25 or the back surface 24 of the light guide plate 21.

  As a specific configuration example of the light diffusion portion R, it is conceivable to form fine irregularities smaller than the wavelength of light emitted by the light emitting diode in the light source 11 on the surface of the light guide plate 21 in the light diffusion portion R. Here, the fine unevenness is surface roughness according to Japanese Industrial Standard JISB0601, and in particular, the average height can be adopted as a reference for the fine unevenness. The light diffusing portion R does not necessarily have to be formed with fine irregularities in the entire region, and may include fine irregularities larger than the wavelength of light emitted from the light emitting diode.

  As described above, a general white LED in which a blue light emitting diode that emits blue light is sealed with a transparent resin to which a yellow phosphor that is excited by the blue light and emits yellow light is added is used as the light source 11. When used, the fine irregularities formed in the light diffusion portion R are formed smaller than the wavelength of the blue light emitted by the blue light emitting diode. For example, since the wavelength of blue light is 430 to 490 nm, irregularities smaller than 430 nm are formed on the surface of the light guide plate 21.

  Note that the color unevenness of the planar illumination device 10 does not occur uniformly in the effective emission region E, but may occur locally, and the amount of occurrence thereof is not constant. For example, color unevenness generated in a region near the end surface 23 tends to gradually increase as the distance from the light incident end surface 22 increases. Therefore, in order to match the tendency of color unevenness, the light diffusion portion R preferably has a transition region in which the area density of fine irregularities gradually increases as the distance from the light incident end face 22 increases.

  Next, an example of a method for forming fine irregularities in the light diffusion portion R described above will be described with reference to FIGS.

  FIG. 3 is a schematic diagram showing how fine irregularities are formed in a part 71a of a mold 71 for injection molding the light guide plate 21. As shown in FIG. As shown in FIG. 3, in the example of the method for forming fine irregularities in the light diffusing portion R, in order to form fine irregularities in the light diffusing portion R, one mold 71 for injection molding the light guide plate 21 is used. The unit 71a is irradiated with laser light from the laser light irradiation device 75. Here, a part 71 a of the mold 71 is a region corresponding to the light diffusion portion R when the light guide plate 21 is injection-molded.

  Note that the laser beam irradiation apparatus 75 shown in FIG. 3 is a schematic one and does not limit the apparatus configuration of the laser beam irradiation apparatus 75 used in this step. If a laser beam having an intensity capable of processing the mold 71 can be output, it can be appropriately used as the laser beam irradiation device 75 in this step.

  Here, the intensity of the laser light emitted from the laser light irradiation device 75 is lowered to the vicinity of the processing threshold. Thereby, the part 71a of the mold 71 irradiated with the laser light can process only the shape of the microscopic surface without changing the macroscopic shape.

  FIG. 4 is a schematic diagram showing a state where fine irregularities formed on the mold 71 are transferred to the light guide plate 21. As shown in FIG. 4, the light guide plate 21 is injection-molded using a mold 71 in which fine irregularities are formed in a part 71 a of the mold 71 and other molds 72 and 73. Then, fine irregularities are transferred to the light guide plate 21 in a part 71 a of the mold 71.

  In this way, if fine irregularities are formed on the surface of the mold 71 side where the light guide plate 21 is injection molded, fine irregularities are automatically formed on the surface of the light guide plate 21 when the light guide plate 21 is injection molded. Therefore, it is suitable for mass production of the light guide plate 21.

  FIG. 5 is a schematic diagram showing the operation of the light guide plate 21 manufactured by the above method. As shown in FIG. 5, fine irregularities formed on a part 71 a of the mold 71 are transferred to the light diffusion portion R on the back surface 24 of the light guide plate 21. The average height of the fine irregularities formed in the light diffusion portion R is smaller than the wavelength of light emitted from the light emitting diode in the light source 11. Therefore, when the light emitted from the light emitting diode and the light emitted from the phosphor incident from the light incident end face 22 reach the light diffusion portion R, the light emitted by the light emitting diode due to the effect of Rayleigh scattering (solid arrow in the figure) ) Is more strongly scattered than the light emitted by the phosphor (broken arrow in the figure). In Rayleigh scattering, it is known that the scattering coefficient is inversely proportional to the fourth power of the wavelength.

  As a result, on the emission surface 25 facing the light diffusion portion R, the light emitted from the light emitting diode is easier to pass through the emission surface 25 than the light emitted from the phosphor. This is because there is a bias that the intensity of the light emitted by the phosphor is stronger than the intensity of the light emitted by the light-emitting diode propagating through the light guide plate 21 near the light diffusion portion R (that is, the color unevenness is uneven). When it occurs, this means that the intensity bias can be improved.

  Next, specific examples of fine irregularities created by the above method will be described with reference to FIGS. FIG. 6 is a diagram illustrating an example of an image obtained by measuring the fine irregularities formed on the back surface 24 of the light guide plate 21 with a laser microscope. The image shown in FIG. 6 includes a region where fine irregularities are not formed (upper half region shown without fine shapes in the drawing) and a region where fine irregularities are formed (lower half shown with fine shapes in the drawing). Area).

Figure 7 shows a roughness curve measured in a region not forming fine irregularities, the roughness curve corresponds to L ₁ in FIG. Figure 8 shows a roughness curve measured by forming a fine irregular region, the roughness curve corresponds to L ₂ in FIG. The measurement of the roughness curve shown in FIG. 7 and FIG. 8 is based on the method of JISB0601 mentioned above.

  As can be seen with reference to FIG. 6, in a region where fine irregularities are formed, substantially random fine irregularities are provided on the surface of the light guide plate 21. As described above, a large number of dots protruding from the light guide plate 21 in a hemispherical shape are arranged on the back surface 24 of the light guide plate 21. Even if the fine irregularities on the back surface 24 of the light guide plate 21 overlap these dots, the operation is not affected. On the other hand, when measuring the surface roughness, the roughness curve (cross-sectional curve) is set avoiding the position of the dots so that the unevenness due to the shape of the dots is not mixed. In addition, the number in a figure has shown the number of the vertex at the time of setting a roughness curve.

  As is clear from comparison between FIG. 7 and FIG. 8, the surface roughness is increased in the region where the fine irregularities are formed compared to the region where the fine irregularities are not formed. Here, in order to examine the surface properties in more detail, the roughness parameters relating to the roughness curves shown in FIGS. 7 and 8 are disclosed.

  Table 1 listed below is a roughness parameter related to the roughness curve shown in FIG. 7, and Table 2 is a roughness parameter related to the roughness curve shown in FIG.

  Here, the meaning of each parameter shown in Table 1 and Table 2 is as follows. Details of the calculation method and the like are as described in JIS B0601. Rp is the maximum peak height and represents the maximum value of the peak height in the roughness curve, and Rv is the maximum valley depth and represents the maximum value of the valley depth of the roughness curve. Rz is the maximum height and represents the sum of the maximum peak height and the maximum valley depth of the roughness curve. That is, the relationship of Rz = Rp + Rv is established between the maximum mountain height, the maximum valley depth, and the maximum height. Note that Rt is the maximum cross-sectional height, and this measurement does not distinguish between the reference length and the evaluation length, and therefore coincides with the maximum height.

  In addition, Rc is an average height and represents an average value of the heights of the contour curve elements. Ra is the arithmetic mean roughness, Rq is the root mean square roughness, Rsk is the skewness, Rku is the kurtosis, and RΔq is the root mean square slope. Will be omitted.

  As is clear from comparison between Table 1 and Table 2, in the region where the fine irregularities are formed, the parameter regarding the surface roughness is increased as compared with the region where the fine irregularities are not formed. It can be confirmed numerically that the surface roughness is increased in the region in which the surface roughness is formed as compared with the region in which the fine irregularities are not formed.

  In particular, as shown in Table 2, the average height of the roughness curve in the region where fine irregularities are formed is 0.343 μm, which is smaller than the wavelength of blue light (for example, 430 to 490 nm). It has become. Therefore, the fine unevenness formed on the surface of the light guide plate 21 shown in FIG. 6 scatters blue light more strongly than yellow light.

  Next, with reference to FIGS. 9 and 10, a verification result of the effect for improving the uneven color unevenness described above will be described. FIG. 9 is a diagram showing a chromaticity diagram showing the difference in chromaticity depending on whether or not the present invention is applied, and FIG. 10 is a diagram showing a graph showing the difference in chromaticity depending on whether or not the present invention is applied. .

  Here, the chromaticity shown in FIG. 9 is chromaticity in the CIE color system. That is, the color mixture ratio calculated from the tristimulus values X, Y, and Z of light is shown on the xy plane. FIG. 9 shows only a white region to which the planar illumination device 10 used in the experiment belongs, extracted from a diagram generally called an xy chromaticity diagram. Therefore, in the chromaticity diagram shown in FIG. 9, it is shown that white is more intense as it goes to the lower left, and white is more intense as it goes to the upper right.

  The chromaticity diagram shown in FIG. 9 shows examples of the chromaticity of the surface illumination device 10 after improvement by the application of the present invention (after improvement 1 to 3) and of the surface illumination device before improvement to which the present invention is not applied. Examples of chromaticity (before improvement 1 to 3) are shown. The planar illumination device 10 after the improvement by the application of the present invention is the planar illumination device 10 having the above-described configuration. In particular, the planar illumination device 10 used in this experiment is the light guide plate 21. A light diffusion portion R is provided in a region 20 mm from the end surface 23 on the back surface 24. On the other hand, the planar illumination device before improvement to which the present invention is not applied is a configuration in which the light diffusing portion R is not provided in the planar illumination device 10.

  The chromaticity value of each example illustrated in FIG. 9 is the chromaticity at the end of the effective emission region E, that is, the position closest to the end surface 23 in the effective emission region E.

  As can be seen by comparing the chromaticities 1 to 3 after the improvement shown in FIG. 9 with the chromaticities 1 to 3 before the improvement, the chromaticities 1 to 3 after the improvement are more than the chromaticities 1 to 3 before the improvement. The position in the chromaticity diagram has changed to the lower left. This is because the planar illumination device 10 after the improvement by application of the present invention is more bluish in light at the end portion of the effective emission region E than the planar illumination device before improvement to which the present invention is not applied. It shows that it is white. That is, according to the application of the present invention, it is shown that the color unevenness that the light at the end portion of the effective emission region E becomes yellowish can be improved.

The chromaticity difference shown in FIG. 10 is defined as follows. The chromaticity difference Δxy at each measurement point is the coordinate on the xy chromaticity diagram of the chromaticity at the reference point (x ₀ , y ₀ ), and the coordinate on the xy chromaticity diagram of the chromaticity at each measurement point. (X, y) and determined by the following equation for each measurement point.
Δxy = √ ((x ₀ −x) ² + (y ₀ −y) ² )
The chromaticity difference Δxy measures color unevenness from the viewpoint of color difference in comparison with a reference point.

  In the graph shown in FIG. 10, the horizontal axis represents the distance d (light incident reference distance) in the direction away from the light incident end face 22 in the vertical direction, and the vertical axis represents the chromaticity difference Δxy at the position. . Note that the range of the horizontal axis describes the distance from 50 mm to 105 mm in order to pay attention to the color unevenness of the terminal portion.

  In addition, the graph shown in FIG. 10 shows an example of the chromaticity difference Δxy of the surface illumination device after improvement by the application of the present invention (after improvement 1 to 3) and the surface illumination device before the improvement to which the present invention is not applied. An example of chromaticity difference Δxy of (before improvement 1 to 3) is shown. Here, the structure of the planar lighting device in the first to third after improvement and the first to third before improvement is the same as the verification experiment shown in FIG.

  As can be seen by comparing the chromaticity difference Δxy of 1 to 3 after improvement shown in FIG. 10 with the chromaticity difference Δxy of 1 to 3 before improvement, the chromaticity difference Δxy of 1 to 3 after improvement is 1 to 1 before improvement. The overall value is lower than the chromaticity difference Δxy of 3. This is because the planar illumination device 10 after improvement by application of the present invention is more colored in terms of color difference in comparison with the reference point than the planar illumination device before improvement without application of the present invention. It shows that unevenness has improved.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible.

  For example, in the above-described embodiment, the light diffusing portion R creates a transition region (for convenience, the “first transition region”) that gradually increases as the area density of fine unevenness increases from the light incident end surface 22 as necessary. Have. On the other hand, when the light diffusing portion R is provided in the vicinity of the light incident wedge portion 27 or in the region near the light incident end surface 22 in order to suppress the light incident color unevenness, the area density of the fine unevenness is the light incident end surface. If necessary, a transition region that gradually decreases as the distance from the center 22 is increased (for convenience, the “second transition region”) may be provided. In addition, a region where the area density of fine irregularities increases or decreases in the direction parallel to the light incident end face 22 regardless of the distance of the light incident reference (for convenience, a “third transition region”). You may make it have. Furthermore, in the above-described embodiment, the light diffusing portion R is provided in a strip shape along the light incident end face 22. For example, the outer edge of the light diffusing portion R may be wavy or curved. Good.

  Here, when the light guide plate is formed by the injection molding method, assuming that a gate is provided along an end surface orthogonal to the light incident end surface, according to the distance from the end surface orthogonal to the light incident end surface 22 (light incident). Color unevenness may occur uniformly or non-uniformly (in a direction parallel to the end face 22). Even if the color unevenness of such an aspect is generated alone or mixed with the color unevenness of another aspect (for example, incident color unevenness or terminal color unevenness), the light diffusing portion R according to the present invention is free of color unevenness. Since it can be appropriately provided in accordance with the generated region and the amount of the generated region (for example, by appropriately combining the first to third transition regions), it is possible to realize color uniformity in a high dimension.

  Further, for example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary. Moreover, what comprised the above-mentioned each component suitably combined is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art.

DESCRIPTION OF SYMBOLS 10 Planar illuminating device 11 Light source 21 Light guide plate 22 Light-incidence end surface 23 Termination surface 24 Back surface 25 Output surface 27 Light input wedge part 28 Output part 71,72,73 Mold 75 Laser light irradiation apparatus

Claims (10)

A light source that emits white light including a light emitting diode and a wavelength conversion material that emits light when excited by light emitted from the light emitting diode, a light incident end surface on which the light source is disposed, and a light incident end surface In a planar illumination device comprising a light guide plate having an exit surface that emits incident light,
The light guide plate, the back surface facing the front Symbol emitting surface, said reflecting respectively light emitted by the light and the light-emitting diode wavelength converting material emits, and the light emitting diodes than the light in which the wavelength converting material emits light There light diffusing portion which mainly scatter light emitted is provided,
The light diffusion part is
The planar lighting device is provided at a position corresponding to a region where color unevenness occurs in the light guide plate . The light diffusion part is
The planar illumination device according to claim 1, wherein the planar illumination device is integrally formed of the same material as the light guide plate. A light source that emits white light including a light emitting diode and a wavelength conversion material that emits light when excited by light emitted from the light emitting diode, a light incident end surface on which the light source is disposed, and a light incident end surface In a planar illumination device comprising a light guide plate having an exit surface that emits incident light,
The light guide plate is provided on at least one of the emission surface or the back surface facing the emission surface with a light diffusion portion that mainly scatters the light emitted by the light emitting diode rather than the light emitted by the wavelength conversion material,
The light diffusion part is
The planar lighting device, which is integrally provided with the same material as that of the light guide plate at a position corresponding to a region where color unevenness occurs in the light guide plate. The planar illumination device according to any one of claims 1 to 3 , wherein the light diffusing portion is provided in a region close to a termination surface facing the light incident end surface. The light diffusion section, according to any one of claims 1 to 4, wherein the wavelength conversion material comprises fine irregularities mainly to Rayleigh scattering light which the light emitting diode emits light than light emitting Planar lighting device. The planar illumination device according to claim 5 , wherein the light diffusing unit includes a transition region in which the area density of the fine unevenness gradually increases as the distance from the light incident end surface increases. The light diffusing section, the planar lighting device according to claim 5 or 6, characterized in that it has a region in which the area density of the fine irregularities is increased or decreased along the light entering end face. The planar illumination device according to any one of claims 5 to 7 , wherein the light diffusion portion includes the fine unevenness smaller than a wavelength of light emitted from the light emitting diode. The planar illumination device according to claim 8 , wherein an average height of the fine irregularities is smaller than a wavelength of light emitted from the light emitting diode. The light emitting diode is a blue light emitting diode that emits blue light, and the wavelength conversion material is a phosphor that is excited by the blue light and emits light having a longer wavelength than the blue light. The planar illumination device according to any one of claims 1 to 9 .